The desperate search for a Malaysian jet that vanished with 239 people aboard has been significantly expanded, as frustrations mount over the failure to find any trace of the plane.

The initial zone spread over a 50-nautical mile (92-kilometre) radius around the point where Malaysia Airlines flight MH370 disappeared over the South China Sea in the early hours of Saturday morning, en route from Kuala Lumpur to Beijing.

It's four days since the plane disappeared from radar screens en route to Beijing from Kuala Lumpur with 227 passengers and 12 crew.

Malaysian authorities announced they were doubling the size of the search area to 100 nautical miles.

"The area of search has been expanded in the South China Sea," Civil Aviation Department chief Azharuddin Abdul Rahman told reporters.

He also confirmed the area now covers land on the Malaysian peninsula itself, the waters off its west coast and an area to the north of the Indonesian island of Sumatra.

The vast stretch under consideration reflects authorities' bafflement over the disappearance of the aircraft, with 40 ships and more than 30 planes finding no sign of it.

A girl stands next to a sign board made and written by the public at Kuala Lumpur International Airport. Photo / AP

Anger grows in China

Emotions were running high as Beijing blamed Kuala Lumpur for a lack of information, while tearful relatives of the 153 Chinese passengers aboard voiced frustration with all sides of the response effort.

China said Malaysia needed to "step up" its efforts after authorities admitted they were mystified.

"The Malaysian side cannot shirk its responsibilities," the Global Times newspaper, which is close to the ruling Communist Party, wrote in a scathing editorial.

"The initial response from Malaysia was not swift enough."

A day of conflicting information deepened the anguish of relatives, with tests on oil slicks in the South China Sea showing they were not from the Boeing 777 and reports of possible debris from the flight proving to be false alarms.

Hong Kong's Civil Aviation Department said that a pilot on a flight from the southern Chinese city to Kuala Lumpur had reported seeing "large debris" while flying over Vietnamese waters in the latest sighting to be investigated.

Stolen passport traveler's likeness to Mario Balotelli

As authorities dismiss each potential clue to the whereabouts of the missing Boeing 777, attention has increasingly turned to the identities of the two passengers confirmed to be travelling on stolen European passports.

Late yesterday Malaysian officials said both the men had "non-Asian" features - contradicting previous suggestions otherwise from the country's interior minister.

Asked to explain what he meant, Civil aviation chief Azharuddin Abdul Rahman said they looked like the Italian footballer Mario Balotelli.

Asked by a reporter what they looked like 'roughly', he said: 'Do you know of a footballer by the name of (Mario) Balotelli? He is an Italian. Do you know how he looks like?'

A reporter then asked, 'Is he black?' and the aviation chief replied, 'Yes'.

He declined to elaborate further.

Police chief Khalid Abu Bakar said that one has now been identified, but that he could not reveal his identity beyond confirming that he was not Malaysian.

Who is Mr Ali?

A Thai travel agent who arranged the tickets for the two passengers has now said she had booked the passengers on the flight via Beijing because they were the cheapest tickets, it has been reported.

The travel agent in the resort of Pattaya said an Iranian business contact she knew only as 'Mr Ali' had asked her to book tickets for the two men on March 1.

She had initially booked them on other airlines but those reservations expired and on March 6, Mr Ali had asked her to book them again.

She told the Financial Times she did not think Mr Ali, who paid her in cash and booked tickets with her regularly, was linked to terrorism.

Mr Rahman also said that five passengers who checked in for the flight but who did not board, had had their luggage removed and checked. Nothing untoward was found.

Oil slicks not from Flight 370

The oil slicks found off the coast of Malaysia during the search for Flight MH370 were not caused by the missing jet, authorities have said.

Laboratory analysis on the oil, which was first spotted on Saturday night, found that it had nothing to do with the Malaysia Airlines jet that disappeared almost three days ago, Malaysian officials have confirmed.

Earlier the crew from a Vietnamese jet reported seeing a " possible life raft" floating in the sea around 250 miles off the country's southern coast, only for search and rescue helicopters to later find it was no more than "a moss-covered cap of cable reel".

Speaking at a press conference in Kuala Lumpur this morning, the director-general of Malaysia's Civil Aviation body, Azharuddin Abdul Rahman, said officials were still struggling with an " unprecedented aviation mystery".

"Unfortunately we have not found anything that appears to be objects from the aircraft, let alone the aircraft," he said. "As far as we are concerned, we have to find the aircraft, we have to find a piece of the aircraft if possible."

Malaysian military officials said on Sunday that the plane, a Boeing 777-200ER, may have turned back from its scheduled route shortly before vanishing from radar screens.

Mr Rahman said officials had set no time-frame for the search and referred to the search for Air France flight 447 which went missing in 2009 on route from Rio de Janeiro to Paris, killing all 228 aboard.

It took investigators two years to locate the black box recorders and three years to piece together what happened. A report eventually blamed a combination of technical failure and pilot error.

"The experts have said this is a very big area for us to cover," Mr Rahman said of the area currently being searched. "We all have to work together to find this aircraft... It will take as long as it takes to find the aircraft."

- Independent, Daily Mail

Thousands of Kiwi travel papers stolen every year

Thousands of New Zealand passports are stolen each year and are a target for criminals and international fraudsters because of their state-of-the-art security features and strong international reputation.

Last year, 2117 New Zealand passports were reported stolen with slightly more being taken here than overseas as thieves attempted to use them for travel and identification.

Department of Internal Affairs general manager of passports David Philp said the number stolen represented 1.66 per cent of the total passports issued each year, which had declined from 3.24 per cent in 2008. Once a passport was reported stolen, it was cancelled and could not be used.

Mr Philp said the New Zealand passport was one of the most secure in the world and therefore generally received a lower level of scrutiny on international borders.

"Fraudsters and thieves target the New Zealand passport because of its high security reputation and the trust other countries have in it."

New Zealand passports have in the past been stolen and tampered with so the names and details of the New Zealand citizens remained legitimate but the photographs were of other people.

There has been criticism internationally that not enough countries use an Interpol database to check if passports being used are stolen - but Immigration New Zealand was unable to verify how often it used the system.

Immigration New Zealand would only tell the Herald it had access to Interpol through the police.

Border operations manager Karen Urwin was confident robust systems were in place to detect the use of false or stolen passports.

The system validates passengers' travel to or through New Zealand by screening its database against an airline's system before travellers are allowed to board. Passengers can be stopped from boarding because an alert has been recorded against their name or passport number, they do not have the required visa to enter New Zealand or the passport they are using is recorded as being lost or stolen.

Ms Urwin said high-risk passengers were identified by a team at Auckland Airport that profiled and analysed information through the airline reservation system and the department's own information systems.

If a passenger was identified as high-risk, they were intercepted and interviewed by an Immigration staff member to decide whether they could continue with their travel.